1. Field of the Invention
The present invention relates to an interchangeable lens (lens unit), a camera to which the interchangeable lens is attachable and from which the interchangeable lens is detachable, and an image-pickup system that includes the interchangeable lens and the camera.
2. Description of the Related Art
Japanese Patent Laid-Open No. (“JP”) 8-129199 proposes an image-pickup system configured to set a high communication speed or communication clock frequency between the camera and the interchangeable lens after it is confirmed that the interchangeable lens is compatible with that speed. JP 7-203116 proposes a radio facsimile machine configured to set a low communication speed when the received voltage level is low and a high communication speed when the received voltage level is high.
The method disclosed in JP 8-129199 sets a high communication speed while maintaining the voltages of the communication terminals of the interchangeable lens and the camera, and the method disclosed in JP 7-203116 sets a high communication speed when the received voltage level is high. Therefore, the number of charges/discharges increases in the communication terminals and a power consumption and a radiation noise increase.